LLC Converters and Control Methods Thereof

Abstract

An LLC converter includes an LLC resonant tank, a first synchronous rectifier and a synchronous rectification controller. The LLC resonant tank includes a primary winding of a transformer including a first secondary winding. The first synchronous rectifier is connected in series with the first secondary winding through a first detection node and between an output power line and an output ground line. The synchronous rectification controller draws current from the first detection node and to raise an operation power source on a filter capacitor supplying power to the synchronous rectification controller.

What is claimed is: 
     
         1 . An LLC converter, comprising;
 a square-wave generator with two power switches connected in series through an input node and between an input power line and an input ground line, for providing a square-wave voltage to the input node;   an LLC resonant tank connected to the input node, including a primary winding of a transformer and a resonant capacitor connected in series, wherein the transformer includes a first secondary winding;   a first synchronous rectifier with a first detection node for connecting the first secondary winding and an output ground line, wherein the first secondary winding is connected between an output power line and the first detection node;   a filter capacitor for providing an operation power source; and   a synchronous rectification controller for controlling the first synchronous rectifier in response to a first detected voltage at the first detection node, comprising a power regulator configured to draw current from the first detection node and to establish the operation power source supplying power to the synchronous rectification controller.   
     
     
         2 . The LLC converter of  claim 1 , wherein the transformer includes a second secondary winding, the LLC converter further comprises a second synchronous rectifier with a second detection node for connecting the second secondary winding and the output ground line, the second secondary winding is connected between the output power line and the second detection node, and the synchronous rectification controller controls the second synchronous rectifier in response to a second detected voltage at the second detection node. 
     
     
         3 . The LLC converter of  claim 2 , wherein the power regulator is configured to draw current from the second detection node for establishing the operation power source. 
     
     
         4 . The LLC converter of  claim 2 , wherein the power regulator comprises a linear dropout. 
     
     
         5 . The LLC converter of  claim 4 , wherein the power regulator comprises a first diode connected between the linear dropout and the first detection node, and a second diode connected between the linear dropout and the second detection node. 
     
     
         6 . The LLC converter of  claim 1 , further comprising a rectifier diode connected between the output power line and the filter capacitor. 
     
     
         7 . The LLC converter of  claim 1 , wherein the power regulator stops drawing current from the first detection node when the operation voltage source exceeds a first predetermined voltage. 
     
     
         8 . The LLC converter of  claim 7 , wherein the LLC converter regulates an output power source on the output power line to a target voltage higher than the first predetermined voltage. 
     
     
         9 . The LLC converter of  claim 1 , wherein the square-wave generator has a half-bridge structure. 
     
     
         10 . A control method in use of an LLC converter, comprising:
 providing a square-wave voltage to an input node of a LLC resonant tank comprising a resonant capacitor and a primary winding of a transformer, wherein the transformer includes a first secondary winding connected in series with a first synchronous rectifier through a first detection node and between an output power line and an output ground line;   providing a synchronous rectification controller controlling the first synchronous rectifier in response to a first detected voltage at the first detection node;   drawing current from the first detection node to charge a filter capacitor and to raise an operation power source supplying power to the synchronous rectification controller.   
     
     
         11 . The control method of  claim 10 , wherein the transformer includes a second secondary winding connected in series with a second synchronous rectifier through a second detection node and between the output power line and the output ground line, and the synchronous rectification controller controls the second synchronous rectifier in response to a second detected voltage at the second detection node. 
     
     
         12 . The control method of  claim 11 , wherein the synchronous rectification controller draws a first current from the first detection node to charge the filter capacitor during a first period, and a second current from the second detection node to charge the filter capacitor during a second period different from the first period. 
     
     
         13 . The control method of  claim 10 , further comprising:
 regulating an output power source on the output power line to a target voltage;   wherein the synchronous rectification controller draws the current to raise the operation power source up to a first reference voltage less than the target voltage, and stops drawing the current when the operation power source exceeds the first reference voltage.   
     
     
         14 . An LLC converter, comprising:
 an LLC resonant tank with a resonant capacitor and a primary winding of a transformer connected in series between an input node and a power line, wherein the transformer includes a first secondary winding;   a first synchronous rectifier connected in series with the first secondary winding through a first detection node between an output power line and an output ground line;   a synchronous rectification controller controlling the first synchronous rectifier in response to a first detected voltage at the first detection node, comprising:
 a power regulator drawing current from the first detection node and to raise an operation power source on a filter capacitor supplying power to the synchronous rectification controller. 
   
     
     
         15 . The LCC converter of  claim 14 , wherein the power regulator comprises a diode and a linear dropout connected in series between the filter capacitor and the detection node, and the linear dropout stops drawing the current when the operation voltage source exceeds a first predetermined voltage. 
     
     
         16 . The LCC converter of  claim 15 , wherein the LCC converter is configured to regulate an output power source on the output power line to a target voltage higher than the first predetermined voltage. 
     
     
         17 . The LCC converter of  claim 16 , further comprising:
 a rectifier diode connected between the output power line and the filter capacitor.   
     
     
         18 . The LCC converter of  claim 14 , wherein the transformer further includes a second secondary winding connected in series with a second synchronous rectifier through a second detection node and between the output power line and the output ground line. 
     
     
         19 . The LCC converter of  claim 18 , wherein the power regulator draws a first current from the first detection node to raise the operation power source during a first period, and a second current from the second detection node to raise the operation power source during a second period different from the first period. 
     
     
         20 . The LCC converter of  claim 19 , wherein the power regulator comprises a first rectifier diode, a second rectifier diode and a linear dropout, the first and second rectifier diode are connected to the first and second detection nodes respectively, and the linear dropout is connected to both the first and second rectifier diodes for raising the operation power source up to a first reference voltage.